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Unsourced comps get challenged.
Evidence the assessor can’t trace is evidence you can’t use.
For Tax Appeals · CompStak One Connect
Build the appeal on comps with a verification trail.
Assessors lean on rent assumptions the market no longer supports. CompStak gives you analyst-reviewed leases and sales, every concession itemized, to show the board where the number went wrong.
Trusted by the leaders in commercial real estate
What tax appeal teams miss without verified comps.
The assessor’s data has gaps.
NOI assumptions go unquestioned because nothing contradicts them.
New cases are hard to find systematically.
Overassessed properties get found one referral at a time.
CompStak One Connect answers each of these with verified, analyst-reviewed comps.
The evidence an appeal needs, and the cases worth filing.
Verify assessor valuations and negotiate lower rates.
Granular comp data lets you cross-check assessor information, rebuild NOI from actual market evidence, and negotiate from strength.
Get StartedComp set · appeal evidence
Office · Class A · Gotham CBD
Starting$82.00
Free rent10 mo
LL work$95.00
NER$75.50
BuildingStartingFree rentLL workNER
400 Mandel Street$82.0010 mo$95.00$75.50
250 Comp Plaza$76.508 mo$80.00$70.20
1 Stak Tower$88.0012 mo$110.00$79.40
Show the rent the space would actually achieve.
Rent Predictor returns the Estimated Starting Rent Today for the subject space with the comps behind it, so you can put a sourced number against the assessor’s rent assumption.
Get StartedStarting rent vs assessed
400 Mandel Street · Floor 28
Est. starting rent$82.00
Assessed$94.50
Gap−$12.50
Comps used14
CompSFStartingNER
Belobrovka Analytics42,000$82.00$75.50
Comp Advisory Group18,400$79.50$73.10
Stak Capital Partners25,000$84.00$77.25
Run the analysis where your team already works.
Query CompStak comps from ChatGPT, Claude, Gemini, or Copilot through the Agent Connect MCP server, and join them against your own records. Statistics and trends are free; pulling the underlying records counts toward your weekly comp limit.
Get Started“Assemble appeal evidence for 400 Mandel Street: assessed rent vs market NER and the comps behind it.”
Assessed rent is $12.50/SF above Estimated Starting Rent Today. 14 comps support $82.00 starting / $75.50 NER.
SourceRentNERDelta
Assessor$94.50—+$12.50
Comp set$82.00$75.50Base
Rent Predictor and Agent Connect are available on CompStak One Connect.
Ask for the appeal evidence in your own words.
Agent Connect puts CompStak inside Claude, ChatGPT, Gemini, and Copilot. Ask the way you’d ask an analyst, and the work comes back with its source comps attached.
“Build the appeal case for Comerica Bank Tower: comparable Dallas CBD leases with concessions itemized, and the gap to the assessor’s rent assumption of $32.50/SF.”
ReturnsAppeal case + comps
“Find buildings in Downtown Los Angeles where leases signed in the last 12 months are below the assessor’s market rent, for new business.”
ReturnsProspect list
“Assemble sale comps for retail in Los Angeles since 2023, with cap rate and NOI, to support the income approach.”
ReturnsSale comp table
“Summarize free rent and landlord work on Manhattan office leases over 10,000 SF this year, for the concessions argument.”
ReturnsStatistics + distribution
Every field that carries an appeal.
Access verified lease, sale, loan, and property data across major CRE asset types in 105 markets, with the details to analyze markets, value assets, and underwrite opportunities.
Net Effective Rent
Free Rent
Escalations
Tenant Improvements
+ more
Cap Rate
NOI
Price PSF
Buyer & Seller
+ more
Building Class
Size & Floor
Year Built
Landlord
+ more
Lender
Maturity Date
Origination
Loan-to-Value
+ more
Across the asset types you work with:
Office
Retail
Industrial
Multifamily*
Flex
R&D
Land*Multifamily data powered by RealPage
CRE data straight from the source.
Each comp goes through a multi-step data verification process.
400 Mandel Street, Gotham, NY
Belobrovka Analytics · Office
SizeRentTerm
400 Mandel Street, Gotham, NY
Belobrovka Analytics · Office
SizeRentTermNet effective
Verified memberReviewed on intake
One building resolvedEvery party matched
1400 Mandel Industrial PkwyHeld for review
Deal participantsProperty record
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Community Sourcing
40,000+ verified CRE professionals at brokerage and appraisal firms submit comps daily. Transaction data is received and reviewed multiple times.
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AI & Machine Learning
Machine learning and statistical anomaly detection flag figures outside the expected range for the market and building. CRE Ontology resolves the address to one building and matches every party on the deal to a verified entity. Flagged records are held for review.
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Analyst Verification
Our team of CRE research analysts review and verify data daily. They cross-check each transaction against deal participants and property records. Data is never estimated or blindly added to the system.
See CompStak One Connect in action.
Find overassessed properties and build the evidence behind the appeal.
Get StartedHow other CRE teams use CompStak.
Questions about CRE data for tax appeals.
What evidence supports a commercial property tax appeal?
Comparable leases with concessions itemized, and sale comps with cap rate and NOI, each carrying a verification trail the assessor can check.
How do I find overassessed properties?
Search recent leases against the assessor’s market rent assumption for the same submarket and building class. Where signed rents sit below it, the property is a candidate.
How does CompStak verify its comps?
Every comp is processed by a multi-step data verification system, including machine learning algorithms, statistical anomaly detection, and a team of CRE data analysts. Read more about our data standard.
What does CompStak One Connect add for appeal teams?
Rent Predictor, which puts a sourced number against the assessor’s rent assumption, and Agent Connect, which assembles the case file inside Claude, ChatGPT, Gemini, or Copilot.
How much CRE data does CompStak have?
CompStak has collected 4M+ versions of lease and sale comps across 105 US markets, contributed by more than 40,000 verified CRE professionals and reviewed by CompStak’s analyst team.